Department of Psychiatry, Massachusetts General Hospital and Harvard Medical School, 149 13th Street, Charlestown, MA 02129, USA.
Neuroimage. 2010 Jun;51(2):910-7. doi: 10.1016/j.neuroimage.2010.02.046. Epub 2010 Feb 24.
Coherent fluctuations of spontaneous brain activity are present in distinct functional-anatomic brain systems during undirected wakefulness. However, the behavioral significance of this spontaneous activity has only begun to be investigated. Our previous studies have demonstrated that successful memory formation requires coordinated neural activity in a distributed memory network including the hippocampus and posteromedial cortices, specifically the precuneus and posterior cingulate (PPC), thought to be integral nodes of the default network. In this study, we examined whether intrinsic connectivity during the resting state between the hippocampus and PPC can predict individual differences in the performance of an associative memory task among cognitively intact older individuals. The intrinsic connectivity, between regions within the hippocampus and PPC that were maximally engaged during a subsequent memory fMRI task, was measured during a period of rest prior to the performance of the memory paradigm. Stronger connectivity between the hippocampal and posteromedial regions during rest predicted better performance on the memory task. Furthermore, hippocampal-PPC intrinsic connectivity was also significantly correlated with episodic memory measures on neuropsychological tests, but not with performance in non-memory domains. Whole-brain exploratory analyses further confirmed the spatial specificity of the relationship between hippocampal-default network posteromedial cortical connectivity and memory performance in older subjects. Our findings provide support for the hypothesis that one of the functions of this large-scale brain network is to subserve episodic memory processes. Research is ongoing to determine if impaired connectivity between these regions may serve as a predictor of memory decline related to early Alzheimer's disease.
在无导向的清醒状态下，自发脑活动的相干波动存在于不同的功能解剖脑系统中。然而，这种自发活动的行为意义才刚刚开始被研究。我们之前的研究表明，成功的记忆形成需要在一个分布式记忆网络中协调神经活动，包括海马体和后内侧皮质，特别是楔前叶和后扣带（PPC），被认为是默认网络的固有节点。在这项研究中，我们研究了在认知正常的老年人中，静息状态下海马体和 PPC 之间的内在连通性是否可以预测联想记忆任务表现的个体差异。在执行记忆范式之前的休息期间，测量了在随后的记忆 fMRI 任务中最大程度参与的海马体和 PPC 区域之间的内在连通性。在休息期间，海马体和后内侧区域之间更强的连通性预测了记忆任务的更好表现。此外，海马体- PPC 内在连通性还与神经心理学测试中的情景记忆测量显著相关，但与非记忆领域的表现无关。全脑探索性分析进一步证实了海马体-默认网络后内侧皮质连接与老年人记忆表现之间的关系的空间特异性。我们的发现支持了这样一种假设，即这个大规模脑网络的功能之一是支持情景记忆过程。目前正在进行研究，以确定这些区域之间的连通性受损是否可以作为与早期阿尔茨海默病相关的记忆下降的预测指标。
